Method for producing artificial silk

ABSTRACT

268,393. Bemberg Akt.-Ges., J. P. March 27, 1926, [Convention date]. Addition to 260,564. Ammoniacal-copper cellulose solutions, processes for making filaments from; apparatus for making filaments,-To ensure the proper action of the draining roller when spinning euprammonia silk according to the stretchspinning method described in the parent Specification, in which method the silk is collected in a centrifuge, the grip of the roller on the thread is increased by increasing the arc of contact between the thread and the roller 6, as shown in Fig. 1, or alternatively a plurality of gripping rollers 7, 8, Fig. 2, each suitably driven is employed, or the thread is held on to the roller 9, Fig. 3, by a pressure roller 10, or the diameter of the draining roller is increased. The roller may be ribbed or smooth, and may be made of glass or indiarubber. The thread, after leaving the spinning funnel 1, may be acidified by passage through a channel 4 or a bath 5.

A. HARTMANN ET AL 2,030,985

METHOD FOR PRODUCING ARTIFICIAL SILK Feb. 18, 1936.

' Original Filed Oct. 30, 1926 IIVVENTORS 41/ 1/57 HART/VAN v GOTTHARD mug/50a ATTORNEY Patented Feb. 18, 1936' August Hartmann and Gotthard Bauriedel, Barmen, Germany, assignors to American Bemberg Corporation, New York, N. Y.

Original application October 30, 1926, Serial No. 145,159. Divided and this application August 5, 1931, Serial No. 555,306. In Germany November 2, 1925 2 Claims.

This application is a division of our application Serial No. 145,159, filed October 30, 1926.

Among the numerous methods of producing artificial silk from cellulose solutions, the viscous process and the cuprammonium process accord? ing to the wet stretch-spinning method are the only ones which have finally proved capable of being used technically on a large scale. Whereas however it was possible at an early date in the manufacture of viscose artificial silk to shorten the time and reduce the costs of manufacture by introducing the centrifuge for storing and twisting. the filaments the introduction of the spinning centrifuge to simplify the textile part in the a manufacture of cuprammonium silk has met with difiiculties.

The centrifuge has the advantage that with it it is possible in one operation to obtain a filament which can be wound onto the reel and is twisted in a manner rendering it immediately capable of being used. In the known technical form of the viscose spinning process, the filament is introduced from above into a spinning centrifuge which is rotating at a suitably rapid speed, the filament, owing to centrifugal force, being thrown against the wall of the drum while being simultaneously twisted and collected there in crossed layers in the form of a so-called spinning cake.

According to the wet stretch-spinning process the cuprammonium silk is produced in a stretch spinning vessel, called, in short, a funnel. As is well known a neutral or slightly alkaline bath is used as a rule as a precipitant. The filaments produced in this manner and still containing copper were hitherto collected on reels, rollers, bobbins or the like and acidified with dilute acid, before, or on the reel, rollers, bobbin or the like.

Attempts have been made to combine the treatment of a cuprammonium cellulose solution to obtain artificial silk according to the wet stretchspinning process with the advantage of the centrifuging process. For this purpose the filaments produced before hand in the known stretchspinning vessels were introduced in a manner corresponding to theviscose process into the spinning drum. The filaments were then acidified with dilute sulphuric acid in various ways in the spinning drum and finished in a known manner. Other experiments have shown that a satisfactory product can be obtained by acidifying the filament before the centrifuge and that under tension. For this purpose a drawing device is inserted between the acidifying device and the centrifuge which on the one hand leads the filament to the centrifuge and on the other hand increases, the draught of the centrifuge to ensure the necessary tension.

Accordingly, the invention consists in a process for manufacturing twisted artificial silk from cuprammonium cellulose solutions in which the filament after leaving the spinning device is acidified under tension and thereafter is drawn in and twisted by a so-called spinning centrifuge.

Since any acid adhering to the filament is instantaneously thrown out in the centrifuge the acidifying must be ended before the filament enters the centrifuge. To ensure obtaining this result according to the invention the path of the filament from the spinning vessel to the centrifuge can be extended. This may be done by suitable arrangement of the drawing rollers, for in stance by placing the rollers in an elevated position so that the filament is first raised from the acid bath and then descends to the centrifuge. It is also possible to lead the filament around the drawing roller and so elongatethe path.

The drawing or delivery rollers may be smooth, ribbed o-r serrated. They may be made of glass, porcelain, soft or hard rubber and other acidresisting materials, the same applying to any guiding rollers.

In order to obtain a filament of a uniform titre it is necessary that the filament adheres sufficiently to the drawing device so that it does not a slip. For this purpose a sufficient length of contact between the filament and the roller is necessary. This may be obtained by increasing the angle of contact around the roller, by arranging pressure rollers under the action of a weight a or spring and so on.

Onv the drawing a device according to the invention is illustrated in several forms of execution.

Figure 1 shows a device with an elevated drawing roller.

Figure 2 a device in which the filament passes completely around the drawing roller.

Figure 3 a device with a pressing roller and Figure 4 a device With a drawing roller of increased diameter of special material.

In Figure 1 the filament leaves the outlet opening 2 of the spinning apparatus i, passing through under the reversing rod 3 and the guiding roller 5, both of which dip into the vessel 6 filled with dilute sulphuric acid, up to the positively driven delivery roller 1, from. which the filament passes through the so-called spinning tube 9 to the spinning centrifuge 8.

In the other constructional form shown in Figure 2 the numerals represent the same parts. The acid vessel 6 has the form however of an inclined gutter upon which fall drops of acid.

In the third form shown in Figure 3 again the numerals represent the same parts. But instead of the guiding roller 5 there is arranged a guiding rod 5a of the same character as the rod 3. Further a pressure roller I is rotatably mounted on the free end of a lever l l which is rockable around an axis l2. The roller Ill presses the filament 4 against the positively driven drawing roller 1 by its Weight or if the pressure so produced is not sufficient a spring may be arranged which presses the roller l0 against the roller 1.

In all constructional forms the guiding roller 5 may in some circumstances be omitted. Instead of treating the moving filament with acid at the reversing rod 3 or on the way from this rod to the delivery roller 1, a satisfactory result is also obtained if the delivery roller 1 revolves in dilute acid or if acid is allowed to trickle over it, and it is of advantage if some acid runs back along the filament towards the reversing rod 3.

It is possible to work with one delivery roller alone as guiding device. In this case the filament running onto the delivery roller must be treated with acid or acid allowed to trickle over it. However it is preferable to provide the delivery roller 1 with a filament guide or a reversing rod 3 having a braking action upon the speed at which the filament is taken off, sothat the filament is subjected to a definite high tension between filament guide or reversing rod and delivery roller, and it has been found especially advantageous to acidify the filament at this point and under the tension produced in this way. This tension can be varied by suitably shaping the filament guide or the reversing rod. This tension of the filament may also be increased by inserting suitable guiding or tension rollers 5. The tension can be increased in this way as desired, but has a definite limit, as the filament may otherwise be damaged by the numerous friction points.

Finally in Figure 4 is shown a device according to the invention in which the angle of contact between the filament of the delivery roller 1 is comparatively small but the diameter of roller 1 is so increased that the length of contact between the filament and the roller is suflicient to prevent slipping of the filament in the roller 1. The roller 1 in Figure 4 may also be made of special more adhesive material or may have a covering of such materials. Primarily rubber is a suitable material, but also other acid proof adhesive materials may be used, for instance artificial resin or phenol formaldehyde, condensation products or mixtures from these materials with other acid proof materials, also for such materials a relatively small angle or length of contact is sufiicient to ensure the necessary friction and to prevent slipping.

What we claim is:

1. The herein described method of producing artificial silk, which consists in passing cuprammonium cellulose solutions in the form of filaments through a flowing coagulating bath while stretching the same, thereafter acidifying the filaments thus produced while subjecting them to a further stretching, and twisting the same into a spinning centrifuge.

2. The herein described method of producing artificial silk, which consists in passing cuprammonium cellulose solutions in the form of filaments through a flowing coagulating bath while stretching the same, thereafter acidifying the filaments thus produced while stretching them under a uniform further tension and twisting the same into a centrifuge.

AUGUST HAR'I'MANN. GOTIHARD BAURIEDEL. 

